Links Image in “Catalog” Page to Posts

In your function virtarich_katalog_function wrap the thumbnail with an <a> link tag like this:

function virtarich_katalog_function() {
        global $post;
        $vtr_query = new WP_Query('showposts=10000');
        while ($vtr_query->have_posts()) : $vtr_query->the_post(); ?>

            <div class="col-md-3 ikibro">
            <div class="wpagen-produk">
            <div class="katalog-gambar-center">
                <div class="katalog-gambar"><a href="https://wordpress.stackexchange.com/questions/260406/<?php the_permalink() ?>" title="<?php the_title(); ?>"><?php virtarich_thumb_normal() ?></a></div>
            </div>
            <div class="katalog-title"><?php the_title(); ?></div>
            <div class="katalog-harga">Rp <?php virtarich_harga(); ?><span class="coret"><?php virtarich_harga_coret(); ?></span></div>
            <?php if(get_post_meta($post->ID, "kode", $single = true) != ""){ ?> 
                Kode : <?php echo get_post_meta($post->ID, "kode", $single = true);
                 } ?>
                 <br/>

            <?php if(get_post_meta($post->ID, "habis", $single = true)){ ?>
                <div class="habis senter">habis</div>
            <?php } else if(get_post_meta($post->ID, "stok", $single = true) != ""){  ?>
                Stok : <?php echo get_post_meta($post->ID, "stok", $single = true);?>
            <?php } ?>

            </div>
        </div>

to be more clear this is the line:

<div class="katalog-gambar"><a href="https://wordpress.stackexchange.com/questions/260406/<?php the_permalink() ?>" title="<?php the_title(); ?>"><?php virtarich_thumb_normal() ?></a></div>